Electric switch



My 28, 1940A M. J. JoHNsoN 2,202,207

- ELECTRIC SWITCH Filed may 26, 1937l ORNEY of the actuating Patentes May 2s, 1940 PATENT IOFFICE 2.202.202 ELECTRIC swl'rcn Manfred J. Johnson.

t The Lewis En Naugatnck, Conn., -assignor f' lineel'ing O0 tuchV Conn., a corporation of mpany, Nauga- Connecticut Application May 26, 1937, Serial No. 144,772

12 Claims.

This invention relates to electric switches.,

An object of the invention is to provide anA improved hermetically sealed electric switching device not affected by externalatmospheric or other like conditions.

This switching device is of particular use in aviation, in connection with the retractable landing gears of aeroplanes. For safe air travel, it is important that thel retractable landing gear mechanism function properly, especially when the aeroplane is taking oil', the position of the landing gear known to the pilot of the aeroplane at all, times, the present improved switch is employed in connection with the signalling device in the cockpit of the aerobeing' associated with the landplane', the switch ing gear to be actuated thereby Vfor indicating whether or not the gear is located properly in extended operative position.

The switching device of this invention is not affected by external pressure or water conditions, and no moisture or dirt can enter the switch housing. and corrode the contacts or otherwise affect the circuit, or cause the switch to become inoperative. Also, the actuating movement required to operate the switch can be extremely small, so that any ,slight movement ofthe land-- ing gear from its proper position will be immediately indicated in the cockpit of the plane. Associated with `the small actuating movement to operate the switch are safeguard means whereby the switch is protected from injury even though there be abnormal excessive movement means.

A switch of this type is adaptable for other uses than those in aircraft, wherever operating conditions are such as might interfere with the normal functioning of ordinary switch mechanisms, and wherever positive and reliable operation of the switch is desired. For instance, the present switch may be submerged in water tanks, in connection with floats for starting and stopping motors, or may be employed where exposure t0 the elements at all times is necessary and Where cold or heat is present; it also has use where explosive fumes exist and sparking contacts might be dangerous.

A feature of the present improved switch structure is that it provides uniform and consistently satisfactory operation under the most,v

severe adverse external conditions.

The switching device includes a hermetically sealed housing enclosing an electric yswitch unit,

Ia waterproof assembly for the actuating mechanism of the switch, and a waterproof outlet means or landing. To make (Cl. 20D- 168) for the wires connected with the switch. 'I'he actuating mechanism operating the switch` proper vom an external primary actuator includes' a link for engaging said actuator and extending into the housing of the switch, said link operating through a compression spring and a sealing bellows to throw the switch.

Another feature of the switching device of this vin vention is the provision of'a double seal between the external and internal actuators for the switch unit. According to the embodiment shown, the intermediary actuator or link comprises in itself a sealed unit, as well as functionv ing .to seal the housing of the switch. V

Other features and advantages-will hereinafter appear.

In the accompanying drawing, showing a preferred embodiment of the invention:

, Figure 1 is a longitudinal section of the switch- 'ing device, the seals and actuating mechanism 20 being clearly indicated, 'and partly in section and partly Fig, 2 is a sectional view of Fig. 1. Fig. 3 is a sectional view taken on the line 3 3 26 of Fig. 1. v

As shown in Fig. 1, the device of the present invention comprises a metal box' or housing In, in'which is mounted a switch unit il, and an intermediary actuating mechanism i2. The lower portion Illa of the housing comprises a-I separate plate secured in place by screws lb and sealed by a gasket Iilc, and said plate is provided with an aperture lild through which extends the actuating mechanism i2 operatively connecting 35 the switch unit with an external actuator i3.

The aperture illd is closed on the inside of the housing by a positive watertight and airtight seal, vwhich includes a gasket M, a sleeve I 5 passing through the aperture and having a flange 40 l5a, and a bellows I6 one end of which is secured to the flange I a. The inside wall of the bottom Ilia of the housing is recessed at Ille to admit the flange l5a, and the latter is securely drawn up against the gasket Il and bottom Ita by a nut Il screwed on external threads at the lower end of the sleeve and engaging the exterior of the bottom. 'I'he upper end of the bellows is closed over and sealed by a circular plate I8 which is adapted to engage the switch unit Il to operate same, as will be later brought out. It will be seenthat the housing Ill ishermetically sealed at its lower portionfby this structure.

The intermediary actuating mechanism further includes an externally threaded bushing I9 55 the switch unit being in elevation. taken on the line 2-2 screwed into the sleeve I5 which latter is internally threaded for this purpose, said bushing being locked to the sleeve by a nut 20 as shown, andfunctioning as a close-fitting guide for a plunger 2| engaging the primary actuator I3. 'lhe plunger2| is' operatively connected to the plate I8 by a helical compression spring 22, one end of which engages a flange 2 Ia on said plunger and the other end of which engages the underside of the plate and is positioned thereon by a circular shoulder on the plate. f

It will be seen that upward movement'of the plunger 2| will cause the spring 22 to compress, and this inturn will move the plate I8 upwardly, accompanied by expansion of the bellows I6. When the plunger is released, it will be returned to its initial lowered position under the urging of the spring 22 and bellows I6, both of which are resilient for this purpose.- The plunger is prevented from being completely withdrawn by the ange 2Ia, which engages the upper end of the bushing I9 and serves as a limiting stop.

In order to prevent any water or moisture from leaking into the bellows wherev it might freeze or otherwise cause trouble, the lower end of the bushing I9 is packed by a felt washer 23 saturated in heavy oil and held against the end of the bushing by a nut 24 screwed over the said end. Preferably the bushing I9 has an external flange I9a against which the nut 24 can be tightened.

For adjustment purposes the lower end of the plunger 2| is axially bored and threaded to carry a screw 25 locked by a nut 26. The head of the screw 25 is adapted to directly engage the primary actuator I3, and the clearance between these can be adjusted by turning the screw.

The electric switch unit II is of a well known type described in detail in Patent No. 1,960,020 issued to P. K. McGall, May 22, 1934. This switch has an important operating characteristic in that it requires an extremely small actuating movementvfor operation. The switch includes a movable resilient snap blade 21 adapted to engage a stationary contact 28, these being respectively connected to lead Wires 29 and 30, and the switch blade 21 being operated by a plunger 3| extending through the bottom of the insulating casing of the switch. The plunger 3| requires but small movement to operate the switch, this being in the neighborhood of .001 inch. The upper face of the plate I8 carried by the bellows engages the lower tip of the plunger 3| so that the switch arm 21 will be actuated when the plunger 2| is moved upward in response to movement ofthe primary actuator I3.

The insulating casing of tlieswitch II is secured within the housing I0 by a pair of upstanding arms |0f carried by the bottom plate Illa, as shown.

Operation of the present improved switching device is as follows: Normally the switch II is biased so that the arm 21 engages the c-ontact 28 to keep the circuit closed. For this condition the plunger l2| is-in its lowermost position wherein the ange 2Ia thereof engages the top end of the bushing I9. When upward pressure is applied to the lower end of the plunger 2| by the primary actuator I3 the plunger will move upward to a position as shown in Fig. 1, causing the spring 22 to compress somewhat and raise the plate I8 and expand the bellows. This movement of the plate I8 will operate the plunger 3| so that the switch K 'arm 21 disengages the contact 28, opening the circuit. Because of the retarding effect of the bellows on the spring 22, the plunger 2| will move a greater distance than the plunger 3|, but the movement of each is exceedingly small as already brought out. When pressure is removed from the plunger 2| it will return to its lower position under the urging of the bellows I6 and spring 22, and the switch arm 21 will return to its initial circuit-closing position.

In order to protect the switch I`I from abnormal or excessive movement ofthe plunger 2|, the top face of the plate I8 is provided with a circular shoulder |8a adapted to engage the insulating bottom Ila. of the switch s o that the upward movement of the plate is limited.

Further safety against excessive movement of the plunger 2| is provided by the compression spring 22 operatively connecting said plunger with the plate I8, which spring can compress an ex' tent after the plate I8 has been stopped in its upward movement. Also the lock nut 26 at the lower end of the plunger is preferably so located that it will engage the lower face of the packing nut 24 to limit the upward movement of the plunger.

The top of the housing I0 is provided with an outwardly extending internally threaded boss 32 receiving a nipple 33 to which is secured a metal conduit tube 34 by means of a nut 35, and the leads 29 and 30 are brought out through this nipple connection and conduit tube. The fitting including the nipple 33 seals the top of the housing I0, so that no dirt nor water can enter except through the conduit 34, and this conduit and the wires passing through it are protected at their other terminals to prevent this.

The lower position of the plunger 2| is determined by engagement of the flange 2 Ia. with the upper end of the bushing I9 and this lower position can be changed within limits by screwing the bushing in or out, as desired.

For mounting the switching device, the housing I0 is provided with supporting arms 36 by means of which it may beA secured to any desired structure.

Variations and modications may be made within the scope of this invention and portions of the improvements may be used without others.

I claim:

1. A device of the character described comprising a housing; an electric switch supported in the housing; current supply means from the switch, passing through the housing; means for sealing the housing where the supply means passes through; an actuator for the switch carried within the housing; means for operating said actuator from the exterior of the housing, including a plunger movably carried by the housing and having a portion extending into said housing; means for sealing the housing lwhere said operating means is located including a bellows surrounding'the portion of the plunger within the housing; and an adjustable extension on the portion of said plunger extending exteriorly of said housing for engagement with an external primary actuator.

2. A device of the character described comprising a housing; an electric switch supported in the housing; current supply means from the switch, passing through the housing; means for sealing the housing where the supply means passesI through; an actuator for the switch; means for operating said actuator from the exterior of the housing, including a seal for said housing; and means for preventing. excessive movement of the switch actuator in response to Asmi-.cn being adapted to '9,202,207A of the operating means, in-V cluding a plurality oi' movement-limiting stops means. c

3. A device of the characterdescribed comprising a housing; an .electric switch supported the housing, and an operate in response to relatively small movement of the actuator; current supply means from the switch, passing' through the housing; means for sealing the housing where the supplymeans passes through; meansfor operating said actuator iromithe exterior'of the housing; including a seal for the housing; and means' i'or preventing excessive movement of the switch actuator in response to abnormal movement of the operating means, comprising a yieldable link disposedintermediate said operating means and the switch actuator including a movement-limiting stopA associated therewith. Y

4. A device of the character described comprising a housing; an electric switch supported in the housing; switch, passing current supply means from the passes through; an actuator for the switch; means for operating said actuator from the exterior of the housing, including a seal for said housing; and means for preventing excessive movement of the switch actuator in response to abnormal movement of the operating means, including a yieldable link-connected with the operating associated with said means.

5. A device vof the character described, comprising a housing; an electricswitch Asupported in the housing, comprising a stationary contact,-

` .a snap-arm for engaging said contact, and an actuator for said arm, said arm being adapted to operate in response to small movement of thev actuator; current supply means from the switch, psing through the hou'sing; means for sealing the housing where the supply meansy passes through; means for operating said actuator from the exterior oi the housing, including a. seal ifor the housing comprising a bellows one end of which engages the switch actuator; and means carried within said bellows and associated with said operating means i'or preventing excessive movement of the snap arm in response to abnormal movement oi the operating means.

6. A device of the character described come prising a housing; an electric switch supported in the housing; current supply means from the v switch, passing through the housing; means for sealing the housing where the supply means passes through; an actuator for the switch; means for operating said actuator from the exterior of the housing,

the housing where said operating means is 1ocated; and stops associated with the housing and plunger for limiting movement of the latter in each direction.

7. A device of the character described comprising a housing; an electric switch supported in the housing; current supply means from the switch, passing `through the housing; means for sealing the housing where the supply means passes through; an actuator for the switch; means for operating said actuator' from the exterior of the housing, including a plunger movably carried by the housing; means for sealing the housing where said operating means is located; and stops associated with the housing and lated.

actuator therefor, said through the housing;- means for; sealing the housing where thesupply means means and a movement-limiting stopincluding a plunger mov-' ably carried by the housing; means for. sealing each direction, one of said stops being adiustableu so that the throw oi the'plunger can be regus. A devices: the character described, comprising a housing; an electric switch supported in the housing; current supply means for the l plunger for limiting movement of the latter switch passing through the housing; means i'or sealing the housing passes through; an means for operating said actuator from the exterior ci' the housing, said means including a plunger movably carried by the housing and a yieldable llnk'connected with the plunger; means i'or sealing the lhousing where' said operating means is located; and stops associated with the housing and plunger i'orlimiting movement'oi'v the latter in each direction, including astop adjacent the switch actuator for "preventing excessive movement of the e in response to abnormal movements oi the plunger.

9. A device of the-character described comprising a housing having an aperture in one oi' its walls; an electric switch supported in the housing; current supply means from the switch,

where the supply means passing through the housing; means for sealing the housing where 'the supply means through; an actuatori'or the switch; a bellows carried by the housing, one end of which bellows engages the switch actuator and the other end of the bellows being secured over the aperguiding said plunger for axial movement in said aperture, including a bushing adjustably mounted in the aperture; and movement-limiting means carried by the plunger and saidl b y 10. A device of the character described comprising a housing having an aperture in one of its walls; an electric switch supported in the housing; current supply means from the switch. passing. through the housing; means for sealing the housing where the supply means passes through; an actuator for the switch; a bellows carried by the housing, one end of which bellows engages the switch actuator and the other end of thebellows being secured overY the aperture in the housing to separate the interior of the latter from said aperture; a plunger extending through the aperture in the housing; a compression spring connecting the plunger with the bellows; means for movement in said aperture, including a bushing adjustably mounted in the aperture; and moveaperture in the housing so that the bellows sep ara'tes the interior of the housing from the aperture; a projection carried bythe plunger-engaging end of the bellows, adapted to engage the actuator for the switch;-

guiding said plunger for axial engaging the ends of" ment-limiting means carried .by the plunger and insulating casing of the switch to limit movement ot the bellows; a second plunger operatively onnected to the bellows and extending throug the aperture in the housing; means for guiding said second plunger for axial movement in said aperture, including a bushing adjustably mounted in the aperture; and movement-limiting means carried by the plunger and engaging the ends of said bushing.

12. A device of the type described, comprising a housing; an electric switch supported in the housing; current supply means from the operating link; and a second seal exterior of the l0 iirst between the link and the housing.

MANFRED J. JOHNSON. 

